I had a 25ft walkaround with twin 200's and a 9.9 high thrust 4-stroke yamaha,it pushed the boat just fine up to around 3 footers,wind/waves bigger then that and you would have to run the big motor to get turned into the waves.look into what a "high thrust"motor is equal to,from what I have been told,it is equal in pushing power to a 20hp,believe its cause of the prop size.what ever you go with,go with a 4-stroke,so smooth,quiet,and no fumes,like in a 2-stroke.also,you can use a control king instead of a control box and cables,controll king gives you precise trolling speeds.